The variety of substrates that emulsion adhesives are required to bond is extending, for example to bond polypropylene, polyethylene and polyester films in the packaging industry. There is a general requirement for emulsion adhesives to exhibit improved properties on non-polar, difficult to stick substrates. Improvements would be enhanced adhesion, cohesion, heat resistance and use without additional plasticizer.
Pressure sensitive adhesives provide immediate adhesion between surfaces placed in contact and subject to pressure, usually the latter is low and can be applied manually. Adhesives of this class are capable of providing adhesion to a surface without the necessity of activation by heat or solvents and have sufficient internal cohesion to ensure the layer of adhesive material does not rupture before the adhesive/surface bond. The ability to give immediate adhesion is usually expressed as "tackiness" and it is normally desirable to obtain as much tackiness as possible without losing any substantially amount of cohesion, is internal strength.
The use of the above adhesives occurs in a wide range of industries, e.g. flooring, packaging, laminates, tapes and labels, but there is a general requirement to improve the properties of such adhesives to allow their use with the more non-polar surfaces. These are exemplified by the polymers polypropylene, and polyethylene.